1. Field of the Invention
The present invention relates generally to moving multiple automated vehicles, and, more particularly, to a control system and method for moving an automated vehicle along an automated electrified monorail under central control.
2. Statement of the Problem
Conventional automated electrified monorail (AEM) systems, typically, contain a monorail, a number of vehicles that move along the monorail and control electronics that control the movement of the vehicles along the monorail. The monorail is an industry standard rail having an I-type cross section. In most applications, the monorail is installed overhead on a beam or suspended from the ceiling. This overhead configuration allows the vehicles to move along the monorail and perform tasks without being impeded by obstacles located at the floor level.
The vehicles contain a suspension system that connects the vehicle to the monorail. The suspension system contains wheels that contact and move along the monorail. Typically, an electric motor is attached to the wheels to propel the vehicle along the monorail. The electrical power for the motor is provided by a number of bus-bar-type power conductors that are hardwired and physically attached along the perimeter of the monorail. Typically, electrical power is provided by four power conductors (three-phase power and a ground wire). The motor contains electrical connectors that provide electrical contact to the power conductors as the vehicle travels along the monorail.
The conventional AEM system has electronic control equipment that is used to instruct the vehicle to move along the monorail. The control equipment usually contains a number of bus-bar-type control conductors that are hardwired and physically attached along the perimeter of the monorail with the power conductors. Typically, conventional AEM systems require about eight to twelve conductors for controlling and powering the vehicles. A predetermined number of the control conductors are used to control the movement and speed of the vehicle while the other conductors may be used to control the vehicle while performing a variety of other functions. At a first end, the control conductors are connected to a system controller that determines the voltage that is to be applied to the control conductors. Along the length of the monorail, the control conductors make contact with the vehicle electronics which contain electrical connectors that electrically contact the control conductors as the vehicle moves along the monorail.
In these systems, the vehicle control electronics are typically hardwired on the vehicle. The control electronics provide vehicle control by interpreting the voltage applied to the control conductors. This interpreted voltage is translated into an applied motor voltage. Accordingly, the electric motor moves the wheels corresponding to this applied motor voltage.
When the vehicles are required to change speeds, for example around curves or known obstacles, these conventional AEM systems require physical cuts in the control conductors, thereby providing movement zones having a specific voltage. Such movement zones are created by physically cutting the control conductors into separate electrically isolated sections. Each section becomes a movement zone and must be separately connected to the system controller which controls the voltage applied to the conductors in the zone.
Installation of conventional AEM systems is typically expensive and labor intensive because these systems require eight to twelve conductors including control and power conductors to be manually installed and routed along the perimeter of the monorail. In addition to the installation expenses, the creation of movement zones on the monorail also are labor intensive and expensive requiring manually cutting and electrically isolating the section conductors at specified locations along the monorail and connecting each separate section to the system controller. After installation, modification of the AEM system, particularly moving the movement zones from one location to another, is difficult because the hardwired conductors must each be disconnected from the system controller and reconnected at the new location. However, if the size of the monorail is changed, all the control conductors must be removed and reinstalled since these conductors have been physically cut to create the movement zones.
Additionally, aside from moving the monorail, relocation of the movement zones on an existing monorail presents a variety of problems. Since the control conductors have been physically cut to create movement zones, any relocation of these zones on an existing monorail requires removal of the old conductors and installation of new conductors. In addition, the new conductors must be physically cut and electrically isolated to create the movement zones newly desired location. The modification and installation of the conventional AEM systems can become even more expensive if the AEM system is installed or modified in an enclosed structure that has many obstacles to restrict the movement of the installation workers. Furthermore, this modification is expensive due to the high cost of the materials (wires, cables and cable trays) and due to the labor time that is required to make the modification.
Also, in conventional AEM systems, the control electronics use discrete signals which limit the amount of data that is capable of being transmitted over the control conductors. Accordingly, to increase the amount of data that can be transmitted, the conventional AEM systems require that additional control conductors be added to the monorail. These additional conductors also require labor intensive and expensive installation and modification.
Another problem with conventional AEM systems is found in the hard-wired vehicle control electronics. Since the vehicle control electronics are hardwired to the vehicle, the AEM system must be shut down or the vehicle must be removed from the monorail to reprogram the control electronics. Reprogramming is typically accomplished by physically changing the hard-wired electronics or by changing the program located in memory in a vehicle controller. In either case, the vehicle must be physically stopped for the change to occur.
Finally, conventional AEM systems are equipped with collision devices containing proximity sensors that are located on an arm extending from the vehicle. These proximity sensors prevent the vehicles from colliding during movement on the monorail. These conventional collision devices have a detection range that is limited to the length of the arm on which the proximity sensor is positioned.
Therefore, a need exists for an AEM system that is easier and less expensive to install than present systems, and an AEM system that is readily adaptable to change and modification. In addition, a need exists for an AEM system that allows for uncomplicated physical relocation or modification of the movement zones. A need exists for an AEM system that communicates significantly more data that conventional systems. Also, there is a need for an AEM system that allows for vehicle program changes that do not require the entire AEM system to be shut down or vehicles to be removed from the monorail. Finally, a need exists for a vehicle having a collision avoidance system where the detection range is not dependent upon the length of a sensor arm.